code: def _compute_sphere_overlap(d, r1, r2):
      """
      Compute volume overlap fraction between two spheres of radii
      ``r1`` and ``r2``, with centers separated by a distance ``d``.
  
      Parameters
      ----------
      d : float
          Distance between centers.
      r1 : float
          Radius of the first sphere.
      r2 : float
          Radius of the second sphere.
  
      Returns
      -------
      fraction: float
          Fraction of volume of the overlap between the two spheres.
  
      Notes
      -----
      See for example http://mathworld.wolfram.com/Sphere-SphereIntersection.html
      for more details.
      """
      vol = (
          math.pi
          / (12 * d)
          * (r1 + r2 - d) ** 2
          * (
              d**2
              + 2 * d * (r1 + r2)
              - 3 * (r1**2 + r2**2)
              + 6 * r1 * r2
          )
      )
      return vol / (4.0 / 3 * math.pi * min(r1, r2) ** 3)
  
file_path: scikit-image/skimage/feature/blob.py
imports: import math
  import numpy
  import scipy.ndimage
  from scipy import spatial
  from .._shared.filters import gaussian
  from .._shared.utils import _supported_float_type, check_nD
  from ..transform import integral_image
  from ..util import img_as_float
  from ._hessian_det_appx import _hessian_matrix_det
  from .peak import peak_local_max
label_desc: Use image node_id 2 for calling a global function with example usage: _compute_sphere_overlap(d, r1, r2) and returns: unknown